Large deposits of hydrocarbonaceous fluids, such as crude oil, are known to exist in subterranean formations throughout the world. In the past, these fluids were recovered from the formations until the natural energy (e.g., pressure) of the formation expired, at which point the formation was typically abandoned. This primary recovery typically produced as little as 15%-25% of the hydrocarbonaceous fluids within the formation, with the large majority of hydrocarbons left unrecovered, because the economic cost of continued production exceeded the value of the quantity of hydrocarbonaceous fluids recovered. As the value of hydrocarbonaceous fluids increased, secondary recovery processes became economically justifiable for use to increase production from formations.
Secondary recovery may include, for example, a pumping operation that draws previously unrecoverable fluids to the surface. However, these processes vary greatly, and processes that enable successful recovery from one or more formations may not be economical and/or successful when used in conjunction with other formations. In addition, the capabilities of secondary recovery methods are limited. For example, formations that contain hydrocarbonaceous fluids with a low specific gravity, and/or high viscosity, and possess little or no natural energy may be unaffected by secondary recovery. In the absence of formation pressure, even fluids of average viscosity and specific gravity are difficult to produce through secondary recovery methods, without the addition of external energy to the formation.
As such, a great deal of attention has recently been given to various methods of tertiary recovery. Logically, an abundance of tertiary recovery processes consider energy-based techniques that increase the temperature (i.e., reduce viscosity) and/or the pressure of the producing formation, thereby increasing flow. For example, “fire flooding” employs the technique of burning oil “in situ” or within the formation, thereby heating the formation and pressurizing the formation with resultant hot combustion gases.
Gas injection is another example of a tertiary process. Under injection pressures, CO2 gas may be solvent with hydrocarbonaceous fluids, which increases the actual volume of the fluids and also reduces specific gravity and viscosity. Thus, the solvency of the injected gas provides increased formation pressure and less viscous hydrocarbonaceous fluids. CO2 injection into the formation also causes the hydrocarbonaceous fluids to “break out” of the formation matrix, and thereby further promotes increased production. Nevertheless, many tertiary processes, such as gas injection, require extensive and/or cost-prohibitive surface equipment and operations, and may also cause damage to the producing formation that hinders or terminates future production ability.
Some economical tertiary processes include introducing an electric current into the producing formation to cause exothermal heating of the surrounding formation, which lowers the viscosity of hydrocarbonaceous fluids and stimulates flow. Typically, electrodes are connected to an electrical power source and are positioned at spaced apart points within the producing formation, whereby single electrodes are usually disposed in a corresponding wellbore that penetrates into the producing formation. When current passes between the electrodes and/or through the formation, high resistance of the formation causes power to dissipate, which results in a power loss that heats the producing formation and hydrocarbonaceous fluids. However, this process is generally limited to the immediate area involved in the heating process, and is uneconomical and inefficient.
There is a need for economical and readily usable enhanced recovery systems and methods, which beneficially use an electrochemical reaction, but do not require constituent elements within the producing formation. There is a need for an improved process that uses an electrochemical reaction to generate gases that permeate and/or mix with formation fluids, whereby the pressure of the producing formation may be increased and/or viscosity of hydrocarbonaceous fluids reduced, thereby increasing flowability and overall recovery. There is a further need to enhance and optimize recovery over vast and extensive distances of fields.
There is also a need to monitor and optimize systems and methods that use an electrochemical reaction to enhance recovery of hydrocarbonaceous fluids. Other needs include the ability to convert clean renewable energy into ˜100% usable energy.